1. Field of the Invention
The present invention relates to a sliding gate plate which is a part of a nozzle used in a flow amount control for molten metal from a molten metal container.
2. Description of the Related Art
As is conventionally known, a nozzle is widely used in a flow amount control for molten metal from a molten metal container. FIG. 3 is a diagram showing an example of the conventional nozzle.
As shown in the figure, a fixing plate 1 has a through-hole 2 for molten metal at a molten metal discharge portion. A projecting portion (connection portion) 4 used for connecting to an upper nozzle 3 is situated at the molten metal discharge portion of the fixing plate 1. A sliding plate 5 which is in slidably contact with the fixing plate 1 is provided such as to be in tight contact with the bottom surface of the fixing plate 1. A through-hole 6 for discharging molten metal is provided at the molten metal discharge portion of the sliding plate 5, and a projecting portion (connection portion) 8 for connecting to a lower nozzle 7 is situated at a molten metal discharge portion.
In the nozzle having the above-described structure, a projecting portion is provided for each of the fixing plate 1 and sliding plate 5 for the purpose of increasing the adhesive property with respect to the upper nozzle (or lower nozzle) and preventing the suction of air from the non-contact portion.
With the conventional sliding gate plate, the through-hole running through the fixing plate 1 and sliding plate 5 is chemically and physically damaged by the molten metal. In order to avoid this, it is proposed that the sliding gate plate should be made to have a structure shown in, for example, FIG. 4A. FIG. 4B is a perspective view of a cylinder which is an insert ring, that is, a part of the plate shown in FIG. 4A. In short, the plate has a structure in which a cylinder 13 is inserted to a through-hole 12 of a projecting portion 14 of a main body of a sliding gate plate 11. The plate shown in FIG. 4 is a sliding gate plate having a structure shown in FIG. 3, and can be obtained by boring the inner wall of the through-hole damaged by molten metal, and inserting the cylinder into the machined through-hole.
Further, FIG. 5 is a diagram showing another type of sliding gate plate, which consists of a sliding gate plate 15 having both surfaces made flat, and a cylinder 13 having a tapered portion 13a at its distal end tightly fit into the through-hole 12 of the sliding gate plate 15.
However, both types of the above-described sliding gate plates has a common structure in which a cylinder is fit into the through hole of the main body of the sliding gate plate, which has been subjected to a boring process. Consequently, if the through-hole is excessively processed, it is likely that the cylinder slips loosely out of the through-hole of the main body of the sliding gate plate, disabling the use of the plate.